What have you guys found to work best jetting wise for 600 vac secs on a dual top Weiand Tunnel Ram? I have my same carb and intake that was on my old 454 now on my new 468. The jetting that i have in the carbs as of right now are 72's on the primaries and stock metering plate for secondaries. This new motor is a 468 roller motor with about 9.5-1 compression. I plan on sticking it in the water next weekend to see what it does. It seemed to run ok on the trailer while tuning but expect a different scene at the lake with higher RPMs. I'm just curious what you guys say about this jetting for the new motor... Any recommendations??

The original secondary metering plates for an 1850 carb would have been equivalent to a 64 jet.  You can replace the metering plates with larger "jetting" if needed.  I have plates out of a set of 660s that I could loan you for testing if you're up for it.
These would be equivalent to going to a 73 jet for the secondaries. 

As for the primary jetting I'd stay with the 72's for the first day of testing.  That is already a big jump from the 66's that should have been in those carbs originally.

You also want to double check to see what power valves and secondary springs are being used.  I'd recommend the "light yellow" springs and 3.5 or 4.5 power valves.

You really need the aforementioned yellow springs.

The trick to getting these jetted correctly is hitting the mark as far as the low booster velocity, so it will be a false high (numerically), but I suspect with the new motor being able to breathe more air, I would not be surprised if she runs a little "Fat" where it was with the lesser engine.

I would be prepared to go up one, but down two sizes. I would not be at all shocked if the jet sizes need to drop.

If you have an infra red thermometer, you can hit the header tubes and get an idea right away if you are going in the right direction. Typically a 300 degree header temp is in the park... Hotter is leaner...

This is "Ball Parking" it big time, because emissivity is different with every set of headers, but you can "average" it out by moving it around a little, I like to spray a touch of flat black ceramic paint on the header flange and use that..

GT

 510-20-13.pdf (122.23 kB - downloaded 493 times.)

This is all I know...

GT

I'll pick those up tomorrow. Thanks guys for the help 🍻


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